Techniques currently used for on-line sodium analysis are known to have objectionable limitations in respect to the scope of applications possible. Ion selective electrodes, for example, tend to drift, require sample treatment, are affected by several difficult interferences, and are useful generally only when analyzing aqueous process streams or sample matrices. Conductivity methods are not selective and can be used only in specific cases. Accordingly, an improved analyzer for determining sodium on-line, and which would have general purpose utility, is particularly desired for process control applications.